The assembly of rotor blades on wind turbines and their transport to and from is a time-consuming, relatively dangerous and also costly task. Known blade gripping devices often consist of a lifting frame (also referred to as lifting yoke) and a number of straps which are attached around at least part of the rotor blade for carrying the rotor blade and holding the rotor blade in place. Using such lifting yokes is quite time consuming, particularly manual attaching the straps around the rotor blade and to a hook and dismounting the blades from the lifting yoke. Especially for dismounting the blades you have to lift up a service
technician to the assembly height by a basket from which he operates during the disassembly of the rotor blade.
International patent application WO 2011/050999 A1 shows a system for controlling the mounting of a component of a wind turbine to a mounting frame, wherein the component is mountable to the mounting frame by a strap. The system comprises a stable main frame and an automatic strap moving mechanism connected to the main frame. The strap moving mechanism is adapted for moving the strap between an open position for placing a component in the mounting frame and a closed position, in which the strap is wound around the rotor blade by means of a number of beams that temporarily hold an end portion of the strap to lead it from one side of the rotor blade to the other side. For that purpose, the beams are tilted in several tilting directions in order to eventually encompass the rotor blade partially. A camera control system controls the engaging of the strap in an engaging position.
Further, from patent EP 2 107 032 B1 there is known a device for handling containers comprising a pivoting hook and electromagnetic means to attract a ferromagnetic element connected to a support handle.
Such gripping systems are still rather complex to handle.
Patent application EP 2 832 677 A1, which is referred herein, shows a blade gripping device for gripping a rotor blade, in particular a rotor blade of a wind turbine. The blade gripping device shown in the mentioned application comprises a sling and a sling handover mechanism with a sling-conveying element and a sling-receiving element, whereby the preferably automated sling-conveying element is realized to convey a connection means of the sling along a two-dimensional predefined path of travel around a part of the rotor blade, i.e. from an open position of the gripping tool, towards the sling-receiving element, to connect to a receptor of the sling-receiving element, i.e. to establish a closed position of the blade gripping tool in which the sling-receiving element keeps the connection means of the sling within its receipt.
Although the sling handover is done automatically, there is a problem that the receptor itself has to be operated manually, i.e. the connection of the connection means to the receptor of the sling-receiving element still has to be done manually.